1. Field of the Invention
This invention relates generally to the field of integrated circuit manufacturing and, more particularly, to a method for forming a rough polysilicon film.
2. Description of the Related Art
In semiconductor manufacturing, it is sometimes desirable to deposit polysilicon film on a substrate in such a way that rough polysilicon results. In dynamic random access memory (DRAM) technologies, for instance, it may be desirable to manufacture a memory cell capacitor using rough polysilicon.
A capacitor having a given lateral area manufactured with a rough polysilicon plate will have a higher capacitance than a capacitor of having the same lateral area manufactured with a smooth plate. The rough polysilicon capacitor has a larger effective dielectric surface area due to the folding of the capacitor dielectric over the rough film. When used in a DRAM memory cell, the larger dielectric surface area increases the memory cell""s capacitance and improves the cell""s charge storage characteristics, thereby improving product performance.
Unfortunately, the use of traditional manufacturing methods to produce rough polysilicon have been generally unsatisfactory because of the widely varying roughness they produce. The instant process results in a more reliable rough polysilicon film that is more easily controlled. Moreover, because the instant process uses etchants and techniques common to the semiconductor industry, this improved process can be readily integrated into modern day manufacturing flows.
In accordance with one aspect of the present invention, there is provided a method for depositing a rough polysilicon film on a substrate. The method includes the steps of introducing reactant gas into a deposition chamber containing the substrate, and enabling and disabling a plasma within the deposition chamber.
In accordance with another aspect of the present invention, there is provided a method for manufacturing a capacitor having a plate formed of rough polysilicon. The plate is formed by introducing reactant gas into a deposition chamber containing the substrate and selectively and repeatedly enabling and disabling a plasma to deposit the rough polysilicon on the substrate. A dielectric layer is formed on the rough polysilicon, and a conductive plate is formed on the dielectric layer.
In accordance with a further aspect of the present invention, there is provided a capacitor that includes a polysilicon plate formed by introducing reactant gases into a deposition chamber and selectively and repeatedly enabling and disabling a plasma at various times during the deposition process. A dielectric film is disposed on the polysilicon plate, and a top plate is disposed on the dielectric film.
In accordance with yet another aspect of the present invention, there is provided a memory circuit that includes a plurality of memory cells. Each of the memory cells has a capacitor. Each capacitor has a plate of rough polysilicon formed by introducing reactant gas into a deposition chamber and selectively and repeatedly enabling and disabling a plasma at various times during the deposition process.
In accordance with a still further aspect of the present invention, there is provided a method for depositing a rough polysilicon film on a substrate. The method includes the steps of: (a) placing a substrate in a deposition chamber; (b) introducing reactant gas into said deposition chamber; (c) creating a plasma; (d) disabling said plasma; (e) pumping a portion of reactive by-products out of said deposition chamber; and (f) repeating steps (c), (d), and (e) until a roughened polysilicon film has been deposited on said substrate.